This project combines the specificity of biomolecular surface recognition with state-of-the-art technologies in biological mass spectrometry (MS) to produce better and simpler analytical tools for researchers in biology and medicine to address phosphoprotein structure and function, both in vitro and in vivo. New classes of active, affinity MS probe element surfaces will be optimized (with bound transition metal ions) to selectively capture and present phosphorylated peptides for subsequent structural evaluation by sequential laser desorption time-of-flight (LD-TOF) mass spectrometry. Emphasis will be focused on the special problems associated with the retrieval and analysis of functional phosphoproteins and fragments that are introduced, produced and/or used within the gastrointestinal tract, most specifically in the case of developing infants and children fed human or bovine milk products. Possible commercial products include l) affinity probe elements suitable for insertion into endoscopes for the visually-directed capture of phosphopeptide analytes in vivo, 2) MS probe kits to facilitate phosphoprotein capture for solid phase phosphorylation, dephosphorylation, and structure analysis by LD-TOF MS, and 3) probe kits to facilitate rapid phosphoprotein "marker" screening and diagnostic assays.